ASTM D2685-11(2019)

Standard Test Method for Air and Carbon Tetrafluoride in Sulfur Hexafluoride by Gas Chromatography

SIGNIFICANCE AND USE
4.1 Air and carbon tetrafluoride (CF4) are two contaminants of interest in sulfur hexafluoride (SF6). Both of these contaminants adversely affect the performance of SF6 when used as an electrical insulating gas. Specification for maximum levels of these contaminants are given in Specification D2472.  
4.2 Gas chromatography is used to separate these contaminants from a sample of SF6 and to determine their concentration.
SCOPE
1.1 This test method covers the determination of air (Note 1) and carbon tetrafluoride as impurities in sulfur hexafluoride.  
Note 1: Nitrogen, oxygen, or any of their mixtures is considered to be air. Commercial grade air or nitrogen is used for standardization.  
1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 30-Sep-2019
• ICS: 71.060.50 - Salts
• Technical Committee: D27 - Electrical Insulating Liquids and Gases
• Drafting Committee: D27.03 - Analytical Tests

Relations

• Replaces: ASTM D2685-11 - Standard Test Method for Air and Carbon Tetrafluoride in Sulfur Hexafluoride by Gas Chromatography
• Effective Date: 01-Oct-2019
• Refers: ASTM D2472-15(2023) - Standard Specification for Sulfur Hexafluoride
• Effective Date: 01-Dec-2023
• Refers: ASTM E260-96(2019) - Standard Practice for Packed Column Gas Chromatography
• Effective Date: 01-Sep-2019
• Refers: ASTM D2472-15 - Standard Specification for Sulfur Hexafluoride
• Effective Date: 01-Oct-2015
• Refers: ASTM D2472-00(2014) - Standard Specification for Sulfur Hexafluoride
• Effective Date: 01-Nov-2014
• Refers: ASTM E260-96(2011) - Standard Practice for Packed Column Gas Chromatography
• Effective Date: 01-Nov-2011
• Refers: ASTM E355-96(2007) - Standard Practice for Gas Chromatography Terms and Relationships
• Effective Date: 01-Mar-2007
• Refers: ASTM D2472-00(2006) - Standard Specification for Sulfur Hexafluoride
• Effective Date: 01-Apr-2006
• Refers: ASTM E260-96(2006) - Standard Practice for Packed Column Gas Chromatography
• Effective Date: 01-Mar-2006
• Refers: ASTM E355-96(2001) - Standard Practice for Gas Chromatography Terms and Relationships
• Effective Date: 01-Jan-2001
• Refers: ASTM E260-96 - Standard Practice for Packed Column Gas Chromatography
• Effective Date: 01-Jan-2001
• Refers: ASTM E260-96(2001) - Standard Practice for Packed Column Gas Chromatography
• Effective Date: 01-Jan-2001
• Refers: ASTM E355-96 - Standard Practice for Gas Chromatography Terms and Relationships
• Effective Date: 01-Jan-2001
• Refers: ASTM D2472-00 - Standard Specification for Sulfur Hexafluoride
• Effective Date: 10-Apr-2000

Overview

ASTM D2685-11(2019) is the internationally recognized Standard Test Method for Air and Carbon Tetrafluoride in Sulfur Hexafluoride by Gas Chromatography, developed by ASTM International. This standard specifies the method for detecting and quantifying air (a mixture of nitrogen and oxygen) and carbon tetrafluoride (CF4) as impurities within sulfur hexafluoride (SF6) using gas chromatography techniques. Proper application of this test is critical in industries where SF6 is used as an electrical insulating gas, as these specific contaminants can significantly affect its insulating properties and operational reliability.

Key Topics

• Detection of Contaminants: The standard focuses on the identification and quantification of air and carbon tetrafluoride in sulfur hexafluoride samples.
• Gas Chromatography: Provides procedures for separating contaminants from SF6 using gas chromatography and determining their concentrations.
• Standardization: Utilizes reference standards-mixtures of known composition-for calibration to ensure accurate measurements.
• Safety and Compliance: Emphasizes the importance of adhering to safety, health, and environmental practices, and compliance with relevant regulations.
• Measurement and Calculation: Discusses repeatability, calibration, and standardization techniques to produce reliable and reproducible results.

Applications

The ASTM D2685-11(2019) standard is essential in the following applications:

• Electrical Power Industry: SF6 is widely used as an insulating medium in high-voltage circuit breakers, switchgear, and other power equipment. The presence of air and CF4 as contaminants can lower dielectric strength and lead to operational failures. This test method ensures the quality and reliability of SF6 used in critical equipment.
• Gas Manufacturers and Suppliers: Producers of high-purity SF6 rely on this method for quality assurance, verifying compliance with industry standards for maximum contaminant levels as described in ASTM D2472.
• Testing Laboratories: Accredited labs use this standard test method as part of their analytical services for clients requiring precise gas composition analysis.
• Regulatory Compliance: Facilities handling or using SF6 gas must demonstrate compliance with relevant specifications and environmental regulations, making this test method indispensable for documentation and reporting.

Related Standards

Professionals utilizing ASTM D2685-11(2019) may also reference the following related ASTM standards:

• ASTM D2472 - Specification for Sulfur Hexafluoride: Establishes maximum impurity levels for SF6 used as an electrical insulating gas.
• ASTM E260 - Practice for Packed Column Gas Chromatography: Details practices for conducting gas chromatography with packed columns.
• ASTM E355 - Practice for Gas Chromatography Terms and Relationships: Provides standardized terminology related to gas chromatography.

Practical Value

By adhering to ASTM D2685-11(2019), industries can ensure the accurate detection of air and carbon tetrafluoride impurities in SF6. Routine testing and monitoring according to this standard help to:

• Optimize the performance and reliability of electrical insulation systems
• Extend the lifespan of SF6-insulated equipment
• Maintain compliance with international quality and safety standards
• Guarantee consistent product quality by minimizing contamination
• Support regulatory compliance and environmental management efforts

Ensuring the purity of sulfur hexafluoride is critical wherever high-voltage electrical equipment depends on its insulating properties. The ASTM D2685-11(2019) test method provides a robust, standardized approach trusted by electrical utilities, manufacturers, and laboratories worldwide.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation:D2685 −11 (Reapproved 2019)
Standard Test Method for
Air and Carbon Tetrafluoride in Sulfur Hexafluoride by Gas
Chromatography
This standard is issued under the fixed designation D2685; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope pounds of air are not separated.The composition of the sample
is calculated from its chromatogram by comparing the area of
1.1 This test method covers the determination of air (Note
the peak of each component with the area of the peak of the
1) and carbon tetrafluoride as impurities in sulfur hexafluoride.
corresponding component on the reference standard chromato-
NOTE 1—Nitrogen, oxygen, or any of their mixtures is considered to be
gram.
air. Commercial grade air or nitrogen is used for standardization.
4. Significance and Use
1.2 The values stated in SI units are to be regarded as
4.1 Air and carbon tetrafluoride (CF ) are two contaminants
standard. No other units of measurement are included in this
standard. of interest in sulfur hexafluoride (SF ). Both of these contami-
nants adversely affect the performance of SF when used as an
1.3 This standard does not purport to address all of the
electrical insulating gas. Specification for maximum levels of
safety concerns, if any, associated with its use. It is the
these contaminants are given in Specification D2472.
responsibility of the user of this standard to establish appro-
priate safety, health, and environmental practices and deter- 4.2 Gas chromatography is used to separate these contami-
mine the applicability of regulatory limitations prior to use. nants from a sample of SF and to determine their concentra-
1.4 This international standard was developed in accor- tion.
dance with internationally recognized principles on standard-
5. Apparatus
ization established in the Decision on Principles for the
5.1 Gas Chromatograph, consisting of a sample inlet
Development of International Standards, Guides and Recom-
system, adsorption column, flow meter, detector, and data
mendations issued by the World Trade Organization Technical
handling system. Ensure that the column material of construc-
Barriers to Trade (TBT) Committee.
tion and sample components are compatible. The apparatus
2. Referenced Documents
must completely separate air, carbon tetrafluoride, and sulfur
hexafluoride as indicated by return of the recorded peak to the
2.1 ASTM Standards:
base line between each successive peak. Chromatograms must
D2472 Specification for Sulfur Hexafluoride
be reproducible so that successive runs of a reference standard
E260 Practice for Packed Column Gas Chromatography
agree on each component peak area or height within 5 %. For
E355 Practice for Gas Chromatography Terms and Relation-
additional information on gas chromatography see Practices
ships
E260 and E355.
3. Summary of Test Method
6. Reagents and Materials
3.1 Air and carbon tetrafluoride are separated physically by
6.1 Cylinder of Helium Gas.
gas chromatography and compared to corresponding compo-
6.2 Reference Standard Mixture—A gas mixture that con-
nents separated under similar conditions from a reference
tains known percentages of air and carbon tetrafluoride in
standard mixture of known composition. The individual com-
helium or air and carbon tetrafluoride in sulfur hexafluoride is
required. The concentration of a component in the reference
This test method is under the jurisdiction of ASTM Committee D27 Electrical
sample should not be less than 50 % nor more than 300 % of
Insulating Liquids and Gases and is the direct responsibility of Subcommittee
the concentration of the corresponding component in the
D27.03 on Analytical Tests.
unknown.
Current edition approved Oct. 1, 2019. Published October 2019. Originally
approved in 1968. Last previous edition approved in 2011 as D2685 – 11. DOI:
7. Calibration and Standardization
10.1520/D2685-11R19.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
7.1 ApparatusPreparation—Preparethegaschromatograph
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
for use as directed by the manufacturer. The following operat-
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. ing conditions have been found satisfactory. However, any
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D2685−11 (2019)
with an integrator, if available.
combination of conditions that result in complete separations
as indicated in the apparatus section will be satisfactory.
A 5 b 3h 3a /n (1)
~ !
(
Carrier gas helium, 40 to 50 mL/min
Column Porapak Q-80/100 mesh or Porapak R 50/80 mesh where:
Column size 6 to 10 Ft (2–3.5 m) by ¼ in. (6.4 mm) nominal
A = average area of each component peak,
Column temperature 40 to 50 °C
b = peak width at half height,
Detector temperature 70 to 80 °C
Sample volume 2 to 5 mL approximately
h = peak height above base line.
Attenuation lowest which will keep peaks on a scale may be varied
a = attenuation,
during run
n = number of peaks included in average, and
Detector thermal conductivity
∑ = summation of the individual pe
...